Metal-based superconductor materials such as NbTi and Nb3Sn are the most common materials today for superconductor wires used in strong magnetic field magnets and so forth. However, because these materials have a very low critical temperature Tc, the temperature at which they can be used is limited to the temperature range of liquid helium, and therefore there has been a big problem associated with quenching the superconductors.
In light of this, there has recently been considerable interest in reports pertaining to the superconductor characteristics of MgB2, which is a boride of magnesium, and the utility of MgB2 as a superconductor material has been examined from various angles.
MgB2 is advantageous in terms of quenching because its critical temperature Tc is a relatively high 39K, and the usable temperature is expected to be expanded to 20K, which is higher than that attainable with conventional intermetallic compound superconductors. However, in order to obtain it as a material that exhibits a high critical current density, the material has to be synthesized in a high-pressure atmosphere (such as 40,000 to 60,000 atm) and, therefore, it holds little promise for application as a superconductor material which now needs to be mass produced at a low cost.
An example of articles disclosing the above prior art is that of Y. Takano, H. Takeya, H. Fuji, H. Kumakujira, T. Hatano, K. Togano, H. Kito, and H. Ihara, Appl. Phys. Lett., 78, 2914 (2001).